There exists a region or an area where it is important for a driver of a succeeding vehicle or an oncoming vehicle to recognize the presence of a motorcycle. Ordinarily, the motorcycle is obliged to turn on a headlight whether day or night. Further, there has been developed a vehicle recognition system which allows other vehicles to recognize the presence of a car and to allow these other vehicles to execute predetermined control processing or, as an opposite case, a vehicle recognition system which allows a car to recognize the presence of other vehicles and to allow that car to execute predetermined control processing. Some of these vehicle recognition systems are now being realized.
In published patent application JP-A-10-115519, a vehicle-use position recognition device is proposed, in which three or more infrared LEDs are arranged on a back surface of a vehicle body of a preceding vehicle, while a camera, mounted on a succeeding vehicle, takes a picture of the rear surface of the vehicle body of the preceding vehicle. A distance between the vehicles or a relative yaw angle is measured based on the infrared image of the preceding vehicle taken by the camera of the succeeding vehicle.
In a recognition/non-recognition system which utilizes infrared rays, it is necessary to recognize accurately in a short time whether the infrared ray source, detected by an image pickup element in the recognition-side vehicle, is a source of normal infrared rays which are emitted from a light emitting element of the recognition-side vehicle or is a mere external light. Further, aspects of a lamp mounted on the vehicle, including mounting position, coloring, brightness and the like are regulated by governmental laws or regulations. Hence, to ensure a high recognition ratio, it is necessary to provide a recognition system for the recognition-side vehicle which possesses a sophisticated image processing function.
Further, in published patent application JP-A-10-115519, it is necessary to arrange the infrared-ray LEDs to be recognized on the preceding vehicle at a plurality of positions. However, a technical drawback occurs when the preceding vehicle or the oncoming vehicle is a motorcycle, in that it is difficult to ensure a mounting space for infrared ray LEDs.
Further, even when the presence of the vehicle to be recognized is recognized, the response of the succeeding vehicle or the oncoming vehicle on the recognition side differs corresponding to a traveling state of the recognized vehicle. Hence, it is desirable to allow the system to recognize not only the presence or the non-presence of the vehicle to be recognized but also the traveling state of the recognized vehicle.